The patent FR 2 793 085 describes an automobile vehicle alternator comprising a stator and a rotor mounted on a shaft. The rotor includes a coil and two pole wheels each provided with a plurality of claws. Interpole spaces that can receive rare earth permanent magnets are defined between the claws of the wheels. The method of manufacturing the rotor includes the step of machining grooves in the claws, once the pole wheels have been assembled, by means of one pass of a tool. This method has a number of drawbacks. For example, as the coil is assembled between the pole wheels before machining the grooves, lubricant is not used during machining, which leads to faster wear of the tool and/or slower machining. Moreover, because of the limitations imposed on the machining tool used, the interpole space between the grooves cannot be made as narrow as required. Finally, swarf produced by the machining can be introduced into the rotor.